This invention relates generally to filters and more particularly, but not by way of limitation, to collapsible filter apparatus for removing particulates from an airstream adapted for use in a paint booth.
Filters, including air filters, are used for a variety of applications. Generally, an air filter fits in a housing and has a filter media which removes undesired particles from a fluid, typically an airstream. Depending on its specific application, the filter media is adapted to remove dust, dirt, paint, fumes and/or other particles.
In paint booths, i.e., paint overspray control or paint arrester applications, a filter is placed in the exhaust airstream of the paint booth or similar structure. Paint spray residual that does not adhere to the article being painted is entrained in the airstream of the exhaust porting from the paint booth. The airstream passes through the filter positioned at an air intake before it is exhausted into the environment.
A few types of filters are commonly used in paint booths and similar applications. One is a rigid, non-collapsible, framed filter. The framed filter is designed to fit snugly in the modular frame of the exhaust airstream of the paint booth. A framed filter typically requires no clips or other additional parts to secure the filter to the modular frame of the paint booth, but does require the use of a rear supporting grid either built into the filter or placed behind the filter in the modular frame to prevent the filter from being drawn through the modular frame into the exhaust duct.
Shipping, storing and disposing non-collapsible framed filters is expensive and burdensome due to the volume of the filters. However, such volume is necessary in an expanded state in order to effectively and efficiently remove and entrain paint from an airstream.
Another type of filter which attempts to overcome these disadvantages is a frameless accordion-type filter media typically manufactured in long sections, i.e., twenty to thirty feet long, and cut to length to fit a particular modular frame of the paint booth. The expandable/collapsible filter medium is formed of paperboard, cardboard and/or honeycomb to create an inexpensive and effective filter means. The collapsible design of these filters greatly reduces the shipping, storage and disposal costs of the filter. However, the filter must be cut and a rear supporting grid typically must be used to secure the filter. Also, clips or wire fasteners must be used to secure the edges of the filter to the modular frame of the air intake.
Another attempt to overcome these disadvantages is illustrated in U.S. Pat. No. 5,252,111 to Spencer, deceased et al., which is incorporated herein by reference. This patent describes a multi-ply expandable filter media formed of honeycomb and a corresponding expandable frame. However, the frame lacks strength because it is not continuous and appears to require the use of a rear supporting grid.
Thus, there is a need for improved filter apparatus which are collapsible, expandable, strong and which do not require the use of clips or a rear supporting grid.